After nearly two years of expensive repair work, Northern States Power d/b/a Xcel Energy (NYSE: XEL) was able to tell the Minnesota Public Utilities Commission on Sept. 3 that restoration activities at the Sherburne County (Sherco) Unit 3 are done.
“We are pleased to report that the Sherco 3 restoration work has been completed,” said the letter to the commission. “We are currently performing pre-operational checks and anticipate initial grid synchronization to occur this week. Once all testing is completed, Sherco 3 will be released for commercial operation and dispatch by MISO. We anticipate the testing will be completed within the next few weeks.”
Xcel said it will continue to provide updates, with the next update expected to be filed later this month. Xcel plans to provide additional information about its root cause analysis report in the next September update.
The 884-MW Unit 3 went off-line in November 2011 while being restarted after a repair shutdown. During testing after the unit restart, specifically the overspeed test, the turbine and generator instrumentation showed vibration levels significantly above normal, and the unit was shut down. The vibration damaged many of the steam, oil, and hydrogen seals in the turbines and generator, and caused a fire.
Sherco is a three-unit, 2,400-MW plant. It burns low-sulfur Western coal from mines in Montana and Wyoming. The plant normally burns more than 9 million tons of coal a year. Northern States Power, after doing a life-cycle study of Sherco Units 1-2, recently said these units are viable for the long-term future.
U.S. Energy Information Administration data shows that coal suppliers to the plant earlier this year were the Absaloka mine in Montana of Westmoreland Coal and the Black Thunder mine in Wyoming of Arch Coal.